Lightning Discharge Characteristics Determined from Extremely Low-Frequency Atmospherics

摘要

The physical description of a median lightning flash is of practical interest in the statistical evaluation of the global electromagnetic noise spectrum and its effects upon communication systems. A technique for locating and investigating the 'fine structure' of individual lightning discharges occurring several thousands of kilometers from a single receiving station is described. The method employs the simultaneous measurement of the vertical and horizontal components of 'slow tail' atmospheric waveforms. Particular example of 'slow tail' waveforms with different characteristics received from lightning discharges occurring simultaneously in widely separated localities are presented. The mean amplitude spectra of the waveforms emanating from the two storm areas are used to calculate the mean source current moment spectra of the waveform sources using zero-order mode theory. The calculated spectra are then compared with data of other workers who employed different measurement techniques. Plans for future measurements necessary to refine the technique are also discussed. (Author)